rathbone



Feb. 2,1926; 1,571,642

J. A. RATHBONE 4 I METHOD OF FORMING MOLDS Filed April 28, 1924 2 Sheets-Sheet l (Juvcnfo:

T/azn 1?. 72a 6550776 Feb. 2 1926. 1,571,642

J.A.RATHBONE METHOD OF FORMING MOLDS Filed April 28, 1924 2 Sheets-Sheet z 331 WWW M attorney! Patented Feb. Z, 192%..

A'IEhl'l' FIQE.

JOHN A. RATI-IBONE, 01F DETROIT,

MICHIGAN, ASSTGNOR TO RATHBONE MACHINE METHOD OF FORMING MOLDS.

Application filed April 23, 1924. Serial No. 709,639.

To (all an/mm it army concern:

Be it known that 1, JOHN A. RATHBONE, a citizen of the United States of America residing at Detroit, in the county of lVayne and State of li fichigan, have invented certain. new and useful Improvements in Methods of Forming li itolds, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to the method of forming molds in molding machines where the sand within the mold flash is compressed by the operation of a ram. It is the object of the invention to overcome a defect in such molds due to the springing of the flask and to this end the invention consists in the method and apparatus as hereinafter set forth.

in the drawings:

Figure l is a sectional elevation of the molding machine;

F gure 2 is a section showing the mold while under the pressure of the ram;

Figure-3 is a similar view when the pres sure of the ram is relieved;

Figures at and 5 are plan views showing diagrammatically and to an exaggerated degree the changes in the flask due to the pres sure of the sand and when relieved from said pressure.

The molding machine which is employed in forming my improved mold may be of any suitable construction, but comprises essentially a stationary frame A, a reciprooatory ram B. a mold 'tlask C and one or more patterns I) arrai'igcd either on one face or on opposite faces of the ram and frame. VJith such a construction when the sand is suddenly compressed within the (task dur ing a quick movei'uent of the ram, the pressure developed within the flask has to a corlain extent the charm-teristics of fluid pressure, heing exerted laterally as well as in the direction of the n'iovement of the rain. Unless the flasks are of a very strut-tion or are reinforced in some manner, this pressure will result in forcing the oprigid conposite walls of the flask outward. When, however, the pressure of the ram is released, the resiliency of the material forming the flask will restore it to its original form, which in turn will bulge the body of sand within the flask so that it will not properly match the complementary portion of the mold.

To overcome the defect just described, 1 form the patterns D with a slightly Warped or convex surface such as to initially produce in the mold a corresponding concave face. With this, when the pressure of the ram is relieved, the bulging effect of the contraction of the flask will change the original concave form into substantially a plane. Thus the complementary mold sections will properly match, as would not be the case without such modification in the pattern form.

The convexity of form of the pattern can be produced either by originally making the pattern in this form or by first making it with a plane face and subsequently springing this face to bulge the central portion thereof. In practice I have found that this latter method is satisfactory and simpler than the former.

What I claim as my invention is:

1. The method of forming molds in molding machines, comprising the ramming of the sand within a mold flask against a pattern warped to compensate for the lateral springing of the flask, whereby the contraction of the flask after removal front the pattern will restore the 'unwarped form.

2. The method of forming molds in molding machines, comprising the ramn'iing of the sand within a resiliently yieldable mold flask against a pattern warped to compensate for the springing of the flask, whereby the contraction of the flask upon removal trom said pattern will restore the unwarped form.

In testimony whereof I allix my signature.

JOHN A. RATHBONE. 

